Manufacture of isoprene.



0. SILBERRAD.

MANUFACTURE OF ISOPRENE.

APPLICATION FILED JAN. 24, 1911.

Patented Apr. 2, 1912.

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OSWALD SILBERRAD, 0F BUCKHURST HILL, ENGLAND.

MANUFACTURE ISOIPRENE.

Application filed January 24, 1911.

Specification of Letters Patent.

Patented Apr. 2, 1912.

Serial No. 604,473.

To all whom it may concern:

Be it known that I, ()swALn SILBERRAD, a subject of the King of GreatBritain and Ireland, residing at The Silberrad Research Laboratories,Buckhurst Hill, Essex, England, have invented certain new and usefulImprovements in the Manufacture of Isoprene, of which the following is aspecification.

The present invention relates to the depolymerization of turpentine oilfor the production of isoprene.

It is well known that when hydrocarbons are subjected to sufficientlyhigh temperature, as by passing through a hot tube, or dropping on to ahot surface, many of them undergo depolymerization. In most cases,however, the yield of any one product is so small, and the productsobtained are so impure, that the process is of'no commercial value as asource of any particular product.

The present invention consists in an improved method of procedure bywhich a larger ield can be obtained.

The invention consists more specifically in subjecting turpentine oil tothe action of heat, for example, by passing turpentine vapor through ahot tube, under suchcondi- 'tions that the pressure in the apparatus inwhich (lepolymerization occurs is considerably below atmosphericpressure.

The invention also consists in the improved process for obtainingisoprene hereinafter described.

The accompanying drawing illustrates one form of apparatus suitable forcarrying the invention into effect.

The apparatus consists of a heating coil a, inside a heating chamber 6,heated by the products of combustion from a number of gas' burners 0,electric pyrometers d, d, being provided to determine the temperature.From the heating coil, a pipe 6 leads to a water cooling coil f,situated in a Water chamber 9. The hydrocarbons condensed in the coil fpass into a vessel It, and the uncondensed vapors pass through a pipe 70provided with a mercury gage Z into another condensing chamber m, fromwhich further hydrocarbons are collected in the vessel or.

The vacuum is produced by means of the vacuum and compressing pump 0,and the vapors passing the pump pass through a cooling coil 7) immersedin brinecontained 1n the chamber 9. Isoprene is condensed in In carryingthe invention into efli'ect, the

turpentine oil to be de olymerized is passed throu h the tube a which isheated to about L50 to 750 C., at a pressure greatly below atmosphericpressure, the suction being produced by the um 0, from which the gasesare delivere an the demiterpcne and the like condensed.

I find it desirable to pass the vapor over a considerable surface ofmetal preferably contained in a metallic tube, as by this means the gaspassing through the tube is brought to an even temperature throughout.

In carrying out the invention according to another example, I may usethe equivalent process of dropping the turpentine oil to bedepolymerized into an evacuated retort heated to redness, the retortbeing connected at one end to a suction apparatus from which the gasesmay be delivered, and the demiterpene and the like condensed.

In the above description of my process I mean by the term turpentine 011turpen tine oil irrespective of whatever its source may be, America,Russia or elsewhere.

I find that by either of the above described processes the yield ofisoprcne can be made to exceed 25 per cent; indeed, with efficientapparatus I have succeeded in rais ing the yield to 50%.

The pressure utilized for the process may be anythin below about 200 mm.of mercury, but have found that the lower the pressure, the beti tr isthe result which is obtained.

The following examples may be given as illustrating the process Example1: 8 liters of turpentine were passed through the spiral heating tube,heated to 550 C., at a pressure of about 5' to 16 mm. of mercury. Thevapor passes through the condensers to the vacuum pump, which deliversthe vapor into the condensing apparatus beyond it, where the morevolatile products of reaction are condensed under pressure. From 8liters of turpentine the following products were obtained:-24 cc. liquidboiling between 5 and 16 0., 723 cc. crude isoorene, 537 cc. benzene,toluene,

xylol, etc., 6686 cc. recovered turpentine. (No sesquiter'pene or resinis obtained). Hence 1314 cc. turpentine was used and yielded 1.83% 24cc. substance of B. P. 5 to 16 C., 55.02% 723 cc. crude isoprene(containing61% pure isoprene), 40.86% 537 cc. benzol, toluol, xylol,etc., 2.29% lossand uncondensable gas.

Example 2: The heating tube was heated to 550 C. at a pressure of from200 to 210 mm. of mercury. From 8 liters of turpentine treated in thisWay, the following products were obtained 2-51 cc. liquid (B. P. .5 to16 (1.), 623 cc. crude isoprene, 829 cc. benzol, toluol, xylol, etc.,6115 cc. recovered tur entine 173 cases uiter ene resin etc.

(B. Pqm er 200 Hence 1885 turpentine was used, and yielded 51 cc.=2.7%:

liquid B. P. .5 to 16 0., 623 Caz-33.0%: crude isoprene, 829cc'.:44.1%=benzol, toluol, -etc., 173 cc.=9.2%=sesquiterpene and .resin,(B. P. over 200 C.) L0ss=10.8%=

uncondensable gas.

I I claim v 1.. A process for the production of isoprene by thedepolymerization of turpentine consisting in heating the turpentine to atemperature of about 450 C. to 750 C. in apparatus which is maintainedat a pressure considerably below atmospheric pressure,'as set forth.

2. A process for the production of iso-' OSWALD SILBERRAD.

Witnesses I W. J. McAniiMs, P. A. OUTHWAITE.

